The Howell Mountains, which are also known as the Mt. George Range, are one of the California Coast Ranges. They divide the Suisun Valley on the east side, from Napa Valley on the west. Historically the southern part of the range has been referred to as both the Sierra de Suscol and as the Sierra de Napa.

The Suisun Valley AVA is an American Viticultural Area in Solano County, California, located just east of the Napa Valley wine region in the Coast Range. It was established as a wine appellation on 27 December 1982, making it among the first AVAs of California, Napa Valley being the first.